In 1995, clinical guidelines for the diagnosis and treatment of patients with immunoglobulin A (IgA) nephropathy in Japan were published by a joint committee of the Special Study Group on Progressive Glomerular Disease, Ministry of Health and Welfare of Japan (Chairman, Kiyoshi Kurokawa, MD), and the Japanese Society of Nephrology (President, Toshihiko Nagasawa, MD). The purpose of this new committee of the Special Study Group on Progressive Glomerular Disease, Ministry of Health and Welfare of Japan (Chairman, Hideto Sakai, MD), is to provide new clinical guidelines for the diagnosis and treatment of patients with IgA nephropathy in Japan. Although this document addresses current clinical practice in Japan, it is hoped that this English version will be helpful to the international community and will facilitate further discussion on this increasingly important disease.